1. Field of the Invention
This invention relates to a method of and an apparatus for measuring refractive characteristics.
2. Description of the Prior Art
In most of lens meters and ophthalmometers available in commercial markets, measurement of refractive characteristics is carried out manually and therefore, much time is required for the measurement and the measuring procedure is cumbersome. On the other hand, automatic lens meters in which measurement is carried out automatically are known from U.S. Pat. Nos. 4,180,325 and 4,182,572. These automatic lens meters are such that the degree of beam deviation is detected from the absolute time during which and the phase at which a spot image light relatively crosses the dark and light portions of the moving boundary locus, and in such lens meters, the fluctuation of the light-reception accuracy by the position of the light-receiving element is decreased while, on the other hand, the presence of movable portions leads to the complexity and poor durability of the apparatus. The measurement principle of the apparatuses shown in the aforementioned U.S. patents is that the degree of astigmatism, the direction of astigmatism and the refractive power are calculated from two astigmatisms in the two ranges of 0.degree.-90.degree. and 45.degree.-135.degree. and one spherical equivalent.